1. Field of Invention
The subject matter disclosed herein relates to a spark plug for use with an internal combustion engine, and more particularly to a spark plug having a structure providing improved flame kernel development and ignitability.
2. Description of the Background
Conventional spark plugs for use in internal combustion engines generally include a tube-shaped metallic shell, an insulator, a center electrode and a ground electrode. The metal shell has a threaded portion for fitting the spark plug into a combustion chamber for the engine. The insulator has a center bore formed therein and is fixed in the metal shell such that an end of the insulator protrudes from the end of the insulator. The ground electrode has a top portion and is joined to the end of the metal shell such that the tip portion faces the end of the center electrode across a gap.
The gap between the center electrode and the tip portion is generally perpendicular to the axis of the spark plug. Similarly, if the tip portions of the center electrode and ground electrode are collinear, a gap axis defined by the center electrode and ground electrode is generally perpendicular to the axis of the spark plug. As a result, the direction of the burn front is limited at least initially in a sideways direction relative to the spark plug axis. The burn front must travel around the ground electrode structure which slows the speed of the burn front. Further, this movement also draws thermal energy from the burn front that could be used to keep the burn front ignited and expanding.
Accordingly, while existing spark plugs are suitable for their intended purposes the need for improvement remains, particularly in providing a spark plug with an electrode structure that facilitates propagation of the burn front.